From: Daniel Karbach Date: Fri, 2 Dec 2016 14:01:35 +0000 (+0100) Subject: sphere/sphere intersection test X-Git-Url: https://git.localhorst.tv/?a=commitdiff_plain;h=48d34439f3d5bc8bebabe9f0ee35970359e61bfa;p=gong.git sphere/sphere intersection test --- diff --git a/src/geometry/geometry.cpp b/src/geometry/geometry.cpp index 002c68f..1d7beeb 100644 --- a/src/geometry/geometry.cpp +++ b/src/geometry/geometry.cpp @@ -302,6 +302,31 @@ std::ostream &operator <<(std::ostream &out, const Sphere &s) { return out << "Sphere(" << s.origin << ", " << s.radius << ')'; } +bool Intersection( + const Sphere &a, + const Sphere &b, + float &dist, + glm::vec3 &norm +) noexcept { + glm::vec3 diff(b.origin - a.origin); + float dist2 = glm::length2(diff); + if (dist2 < std::numeric_limits::epsilon()) { + // origins coincide, use smaller of the diameters for + // depth and pick arbitrary normal + dist = 2.0f * std::min(a.radius, b.radius); + norm = glm::vec3(1.0f, 0.0f, 0.0f); + return true; + } + if (dist2 < (a.radius + b.radius) * (a.radius + b.radius)) { + dist = std::sqrt(dist2); + norm = diff / dist; + dist = a.radius - (dist - b.radius); + return true; + } else { + return false; + } +} + bool Intersection( const Sphere &sphere, const Plane &plane, diff --git a/src/geometry/primitive.hpp b/src/geometry/primitive.hpp index c922506..e785c63 100644 --- a/src/geometry/primitive.hpp +++ b/src/geometry/primitive.hpp @@ -31,6 +31,11 @@ struct AABB { return glm::length(high); } + void Position(const glm::vec3 ¢er) noexcept { + const glm::vec3 halfsize((max - min) * 0.5f); + min = center - halfsize; + max = center + halfsize; + } void Move(const glm::vec3 &delta) noexcept { min += delta; max += delta; @@ -170,12 +175,28 @@ bool CullTest(const AABB &box, const glm::mat4 &) noexcept; bool CullTest(const AABB &box, const Frustum &) noexcept; struct Sphere { + glm::vec3 origin; float radius; + + void Position(const glm::vec3 ¢er) noexcept { + origin = center; + } + void Move(const glm::vec3 &delta) noexcept { + origin += delta; + } + }; std::ostream &operator <<(std::ostream &, const Sphere &); +/// Two spheres intersection test. +bool Intersection( + const Sphere &, + const Sphere &, + float &dist, + glm::vec3 &norm) noexcept; + /// Test for intersection of sphere with double sided infinite plane. /// If true, dist will hold the smaller interpenetration depth and norm /// the respective contact normal. diff --git a/tst/geometry/IntersectionTest.cpp b/tst/geometry/IntersectionTest.cpp index 36cacdf..550c0f2 100644 --- a/tst/geometry/IntersectionTest.cpp +++ b/tst/geometry/IntersectionTest.cpp @@ -325,6 +325,59 @@ void IntersectionTest::testBoxBox() { ); } +void IntersectionTest::testSphereSphere() { + const float delta = std::numeric_limits::epsilon(); + + Sphere a{{ 0.0f, 0.0f, 0.0f }, 1.0f}; + Sphere b{{ 0.0f, 0.0f, 0.0f }, 1.0f}; + float depth; + glm::vec3 normal; + + CPPUNIT_ASSERT_MESSAGE( + "coincidental spheres should intersect", + Intersection(a, b, depth, normal) + ); + CPPUNIT_ASSERT_DOUBLES_EQUAL_MESSAGE( + "bad intersection distance", + 2.0f, depth, delta + ); + // normal can be just about anything + + b.Move({ 1, 0, 0 }); + CPPUNIT_ASSERT_MESSAGE( + "spheres should intersect", + Intersection(a, b, depth, normal) + ); + CPPUNIT_ASSERT_DOUBLES_EQUAL_MESSAGE( + "bad intersection distance", + 1.0f, depth, delta + ); + CPPUNIT_ASSERT_EQUAL_MESSAGE( + "bad intersection normal", + glm::vec3(1, 0, 0), normal + ); + + b.Position({ -1.5, 0, 0 }); + CPPUNIT_ASSERT_MESSAGE( + "spheres should intersect", + Intersection(a, b, depth, normal) + ); + CPPUNIT_ASSERT_DOUBLES_EQUAL_MESSAGE( + "bad intersection distance", + 0.5f, depth, delta + ); + CPPUNIT_ASSERT_EQUAL_MESSAGE( + "bad intersection normal", + glm::vec3(-1, 0, 0), normal + ); + + b.Move({ -1, 0, 0 }); + CPPUNIT_ASSERT_MESSAGE( + "spheres should not intersect", + !Intersection(a, b, depth, normal) + ); +} + void IntersectionTest::testSpherePlane() { const float delta = std::numeric_limits::epsilon(); diff --git a/tst/geometry/IntersectionTest.hpp b/tst/geometry/IntersectionTest.hpp index 4865c88..680d4ca 100644 --- a/tst/geometry/IntersectionTest.hpp +++ b/tst/geometry/IntersectionTest.hpp @@ -17,6 +17,7 @@ CPPUNIT_TEST(testAABB); CPPUNIT_TEST(testSimpleRayBox); CPPUNIT_TEST(testRayBox); CPPUNIT_TEST(testBoxBox); +CPPUNIT_TEST(testSphereSphere); CPPUNIT_TEST(testSpherePlane); CPPUNIT_TEST(testSphereHalfSpace); @@ -30,6 +31,7 @@ public: void testSimpleRayBox(); void testRayBox(); void testBoxBox(); + void testSphereSphere(); void testSpherePlane(); void testSphereHalfSpace();